That's perfectly fine. Don't worry about forgetting words. You will forget them, look them up again, forget them look them up again, eventually they'll stick. Focus on the reading. Don't treat it like a vocabulary lesson. Every day you're here to read, as long as you reach the end you're good, over months you'll realize you learned a lot of vocabs.

At first because the text will be so dense with new words yes it will take a long time to read, that's why I typically only read a short maybe half a page per day. Then gradually increase that as your vocabulary grows over months. The goal should be to encounter say 50-100 new words a day. Notice I said encounter not learn.

Those websites where you look up words are really useful. Make sure they have text to speech and read out loud in the language not in English even if you see the translation in English that's fine.

Also do a lot of listening along with the reading. I usually get myself an audio book and its corresponding text, chop it up into 1 minute and half a page segments, for each segment listen once, then read looking new words up, then listen while reading at the same time a few times, trying to follow a long, looking up any words I forgot, then listen without reading a dozen or so times until I can follow along. Then movd on to the next segment.

Sounds like you're not ready for this stage yet. I thought I could do that with German and failed horribly. I recommend that you get some vocabulary or phrase books. Those are split into sections and you can add those to your list of vocab words. Learn introductions , food, body parts, household items, colors, numbers, etc. What do you often do? Office work? Learn the words for document, report, stapler, etc. Do you travel a lot? Learn airport, train, ticket, etc. Have you heard of Anki? Use it to fully memorize words. Don't just use it for base verbs. Also include conjugations, honorifics, and small sentences. I don't know much about the specifics of the Korean language but I know that it's a difficult language and it'll take some time until you can read native text. When you do, you should start out with music. Songs tend to be repetitive and use the same words so you will start noticing words more and more. Add these words to your vocab. You can repeat this process more and more until you get into websites and TV shows and movies. It will take time and you'll feel discouraged but every language uses more words than others and by learning from these books, you should build up a solid base to the point where you're not clicking on every single word

This might be a dumb question, but the answer you were given that compared to Chinese made me wonder, did you learn the alphabet? A lot of English speakers assume Korean is a symbol based language, like Chinese, and expect to have to learn a whole word by sight. But Korean has an alphabet, and words can be sounded out phonetically. "Reading" words, even if I don't know what they mean, helps me recall meanings and decrease dictionary use for any individual word over time.